Neutralization of sulphonated organic esters



Patented Nov. 24, 1953 NEUTRALIZATION OF SULPHONATED ORGANIC ESTERS Arthur Ira Gebhart, Union, and Joseph Edward Mitchell, East Rutherford, N. J., assignors to Colgate-Palmolive-Peet Company, Jersey City, N. J., a corporation of Delaware No Drawing. Application August 6, 1949, Serial No. 109,074

' 3 Claims. (01. 260-400) "sulphonated material or products, which salts have useful surface-active and detergent properties, a considerable excess. of the sulphonating agent is generally used and the unreacted portion is subsequently neutralized along with the organic sulphonate. Among the most useful of these sulphonates are compounds which include in their molecular structure an ester linkage or grouping Sulphonated esters containing such molecular structure, however, are not stable in an aqueous alkaline medium owing to their tendency to hydrolyze at the carboxy ester or sulfuric acid ester linkage. It is therefore important to carry out the neutralization of such sulphonated esters Without producing undesirable hydrolytic side reactions if satisfactory yields are to be obtained.

Compounds, the water-soluble salts of which have useful surface-active properties, and which are applicable for neutralization in accordance with this invention are, for example, the higher fatty acid esters of lower molecular weight alkylol sulphonic acids, e. g., the oleic acid ester of isethionic acid (the sodium salt being known as Igepon A); higher fatty alcohol esters of sulfocarboxylic acids, e. g., dioctyl sulfosuccinate (the sodium salt being known as Aerosol OT) hydroxy sulphonated fatty acid esters, e. g. the lauryl ester of 2,3 dihydroxy propane sulphonic acid; the sulfuric acid esters of polyhydric alcohols incompletely esterified with fatty acids of high molecular weight, e. g. glyceryl monolaurate sulfate; and sulfates of long-chain alcohols such as prepared by the hydrogenation of fats e. g. dodecanol sulfate (the sodium salt of such higher fatty alcohols being commonly known as Gardinol, Duponol, etc.)

These ester-type compounds, which contain Z hydrolysis in the presence of an aqueous alkaline medium, the rate of-hydrolysis depending upon the pH and the temperature and being relatively rapid at temperatures above room temperature and high pH of the order of 10 and over. Such high temperatures are usually attained during neutralization in commercial practice unless, special precautions are taken. To prevent undue temperature rise during neutralization it has generally necessitated the use of effective cooling means associated with the neutralizing vessel. Where, however, the withdrawal of heat is not maintained at a suificiently high rate during neutralization some hydrolysis takes place, particularly in localized areas of. the reaction mass.

Various attempts have been made to eliminate these undesirable efiects. Some of these involved operating techniques such as rigid and accurate control of the neutralization, and efficacious methods of admixing the reactants, with the view of preventing localized concen tration of alkali or localized overheating.

It has now been discovered that the neutralization of these easily hydrolyzable sulphonated ester compounds, such as result from the sulphonation of substances as described, may be effected without the use of cooling devices at ordinary room temperature or above without encountering objectionable hydrolytic side reactions. Briefly, the improved method of the invention comprises neutralizing the acidic sulphonated mass with an alkaline neutralizing agent consisting essentially .of carbonate sus-' pended in an aqueous-organic vehicle and in which the carbonate is only slightly soluble. The liquid organic constituent of the vehicle is a solvent for the resultant neutralized sulphonate; and is used in such proportion as substantially to protect the neutralized organic product against hydrolysis while assisting in preventing foa1n.- ing. The proportion of water present in the vehicle must be over 15 by volume, and prefera ably at least 25% to promote the neutralization reaction so that the same proceeds smoothly and uniformly to substantial completion. Withoutadvantage over certain prior art methods in that the neutralization can be carried out without the use of cooling means at room temperature or above, for example up to 50 C. or higher, without encountering such objectionable decomposition and hydrolytic reactions as would make the pr oi it e comm rcial value. The temp ature of the reaction is strictly maintained within the desired range by controlling the rate of introducing the acid mix into the alkaline neutralizing material while at the same time making use of the cooling efiect produced by the evolution of carbon dioxide gas throughout the reaction mass. In this manner the necessity of employing external cooling means is avoided. .WhiQh is of com? mercial significance in practicing the. process.

The improved process of the invention, further permits the neutralization to be effected using a mild, inexpensive neutralizing agent, and practically eliminates the danger of causing injury or destruction of the sulphonated compound .or the resultant neutralized sulphonated product. lvl'oreover he neu ra i ation m y b carried ou under ord nary atm spher pressure, nd even in an. open. vess l pr vided the loss of the o g nic solvent. by e aporation is not objectionable.

Th as c a in mat rial fo ne tral zing the sulphonate is suspended, in fine. part1o ,sv in the aq ouseorg n veh clei wh h thcalkaline mat rial i insoluble .or at must on y i htly s ubl Suitable alkalin sub ances in lud t alka i m l a k line ear h m al and-ammon um carbona s. for x mp e. dium carbonate, so..- um bo e po s i m ca bona potassium bicarbonate, calc um carb nate. mag e ium carbonate, ammonium carbonate and ammonium bicarbonate. Mixtures of these compounds may be employed, if desired. 1

Use of these alkaline materials to, neutralize the acidic material in the-aqueousrorganic vehicle, as set iorthabove, makes itpossihle to effect the neutralization without the necessity of ,employing refrigerating means to cool the reactants and/or to prevent the temperature of the reaction mass from rising unduly. Some cooling means may e e p d, h wever, if. d i ed but t same can be dispensed with due to the cooling e ec p duced by th f rmat n of as bubbles throu h t the r ti n. mass.

The cool effect obtained is bel eved t resul at least for the most part, from he ev luti n o the gas in the presence of both water and organic solvent, Free water, for instance, water in excess. of the amount which may be chemically bound as wate of crysta li atio p m te the neutralization reaction, Although the exact nature of the action which the water play dur g neutra zation has not been determined, the presence of free wat z e en in q ant s insuf i e o k to solution all of. the nor anic ulfate b -nroduct formed, makes the reac ion proceed. s oo y and.

unif rmly to substantial c mpl t on Th n s nse f larger amou ts of Water (e a high r than a ratio by volume o wit res t t th o ganic solv nt) s pe mis ible bu the r use of increasin the perc n ge of dec m sition p oducts present n t e fi roduct as evidenced by th in ea d m t f he soluble matte foun in such u sh crease in ether-soluble matter, of course, lowers the percentage of active ingredient (neutralized sulphonatedmaterial) present which for most purposes is undesirable,

The optimum proportion of water employed in the aqueous-organic solvent vehicle to obtain the best results in each case will, of course, depend upon the particular organic solvent used and the chemical nature of the acidic sulphonate material being neutralized. In a typical case, using an alkaline slurry comprising sodium carbonate in a mixture of ethyl alcohol and Water for neutraliz ng an a id mi e comprisin roono of monoglycerides of coconut oil fatty acids and free sulfuric acid, it was found that where the .liquid vehicle of the alkaline slurry comprised approximately by volume of ethyl alcohol the final neutralized sulfate product recovered contained less than about 5% by weight of ether soluble material, On the other hand, it was found that when a like acid mix was neutralized .5.1115 a similar slurry of sodium carbonate, ethyl alcohol and water wherein the percentage of ethyl alcohol was decreased from 50% to 35% by volume, based on the liquid vehicle of the slurry,

the ether-soluble fraction rose above 5% by weight in the finished neutralized product. In general, it is preferred that the aqueous-organic solvent vehicle of the alkaline slurry comprise between about 50% and 7 5% by volume of organic solvent. A higher percentage of organic solvent may b used u der ertain c d on bu ess than 85% by volume must be used in order to keep th wat r 9 1mm 3 15%- The prop tion or uid vehicl n th alkaline slurrm 8- he mixtur 9 l t a r an solvent used in making up the basic mixture for neutralizing purposes, is sufficient to provide a slurry mass which, upon the addition of the acid sulphonate material, will have a consistency such that the mass can be readily stirred or mixed using conventional equipment. The total solids content of the slurry after addition of the acid sulphonate material is kept preferably below abou y w i h s nce expe me t av shown that where, for example, an alcoholewater slurry is utilized to neutralize an acid sulphonate, such as described, the reaction mass becomes too stiff to stir in a satisfactory manner when the total solids amounted to about The proper proportion of liquid vehicle to use in any particular case may be determined by taking a small sample or portion of the acid sulphonate material to be neutralized and admixing it with a stoichiometric amount of the alkali required to neutralize the sample, the alkali material being previously admixed with a measured quantity of the aqueous-organic solvent vehicle which it is desired to use. If the neutralized mass is too stiff to be easily stirred then an alkaline slurry is used containing a larger quantity of the aqueous-. organic vehicle, and such as does not form a stiff unworkable mass during neutralization.

The neutralization process of the invention may be carried out as a batch operation or continuously, and if desired, in the presence of previously neutralized sulphonate material. For example, the process may comprise flowing a stream of the acid mix and a stream of an alkaline slurry mass in confluence then recovering the lecular weight alcohols e. g. ethyl, methyl and isopropyl alcohols are generally preferred for economic reasons, other suitable organic solvents, or mixtures thereof with water may be employed. For example, in place of an alcohol,

a ketone such as acetone or ethers, e. g. dioxane, Cellosolve, carbitol or appropriate mixtures thereof may be used. Further, mixtures of any two or more of the diiferent organic compounds may be used as the organic solvent component if desired.

The neutralization of the acidic sulphonated material may be carried on until any desired pH value of the reaction mass is reached, the pH value in a given case depending largely upon the particular product and how it is to be used. In the preparation of certain detergents, for example the water-soluble salts of the sulfated esters of polyhydric alcohols incompletely esterified with fatty acids, it is generally preferred to provide a neutralized product having a pH within a range of about 5 to 7.

The temperature of the solution after neutralization of the sulphonate material should be adjusted to preferably lie in the range wherein the lay-product inorganic salt has its maximum solubility in water, but not so high as to greatly accelerate the boiling off of the organic solvent or aqueous mixture thereof. Generally the temperature is kept between 25 and 70 C., and, where sodium sulfate is the lay-product salt formed during neutralization, the temperature is preferably maintained between about 30 and 50 C. wherein this salt has its greatest solubility in water. The neutralization is carried out at relatively low temperature, for example below about 40 C., and ordinarily provision is made to prevent loss of the organic solvent during the neutralization, as for example by employing condensing equipment.

At the end of the neutralization step the inor= ganic salt material formed as a by-product of the neutralization may be dissolved or only partly dissolved depending upon the constituents employed and their particular concentration as well as the temperature of the resultant neutralized mass. A liquid-liquid phase separation of the organic and inorganic salts is preferably effected where it is desired to produce a purified organic sulphonate. Thus, by suitably adjusting the temperature of the resultant neutralized mixture and concentration of the organic solvent and water ingredients, the neutralized organic sulphonate, or active ingredient, dissolved in the organic solvent may be made to separate from the higher specific gravity liquid comprising principally an aqueous solution of the inorganic salt. The liquid layers thus formed by one or more phase separations may be drawn off separately and the neutralized water-soluble organic sulphonation procluct recovered from the combined lighter specific gravity layers by evaporation of the organic solvent and water present. For certain purposes, however, it may be desirable to utilize the result ant neutralized sulphonate product as a mixture of organic sulphonate and inorganic salt. Accordingly, by suitably varying the proportionate amount of inorganic salt removed from the neu tralized organic sulphonate material, a detergent may be produced having any desired ratio of active ingredients to inorganic salt.

Where it is desired to produce a solid product this may be done by the use of drying rolls or by heating the mass and flashing off the organic solvent and spray drying the product similarly as in the making of spray-dried soaps. The inorganic sulfate formed during neutralization may be either left as a part of the final product or removed, depending upon the properties desired in the finished product.

. The following examples serve to illustrate the invention, it being understood that the same is not to be restricted specifically thereto.

EXAMPLE I bonate while stirring. The temperature of the solution rises to about 55 C. After cooling the mixture to 35 C. there are added 56 grams of ethyl alcohol (95%). Into this aqueous-alcohol sodium carbonate slurry is introduced slowly in the form of a thin stream while stirring 100 grams of an acid mixture comprising monosulfuric acid esters of monoglycerides of coconout oil fatty acids. (For example as obtained by reacting glycerine, coconut oil, and fuming sulfuric acid, the oil and glycerine being present in the proportions to form the monoglyceride, and the sulfuric acid being of such strength and quantity as will react and form the monosulfate and leave an excess of sulfuric acid in the mixture.) This acidic sulphonated reaction mass, which is commonly referred to as acid mix, is run into the alkaline slurry at such a rate as to maintain the temperature during neutralization to between about 35 and 45 C. After all of the acid mix is added the pH is adjusted if necessary, to about 6.0 to 6.5. The neutralized mass, which is in the form of a thick paste, is heated to about C. to evaporate the alcohol, which is recovered for reuse, and the resultant mass comprising the neutralized organic sulfate material and sodium sulfate is roll dried to provide a solid detergent product.

EXAMPLE II To 70 grams of water in a 1500 ml. beaker there is added 52.5 grams of sodium bicarbonate and 33 grams of sodium carbonate. After cooling the mixture to 35 C., ethyl alcohol is added in the amount of 58 grams and the mixture stirred forming a slurry. Into this aqueous-alcohol slurry is then run slowly, grams of the acid mix described in Example I, the acidic ester being introduced while stirring the mass, and at such a rate as to maintain the temperature of the reaction mixture between about 30 and 45 C.

After all the acid mix is added, grams of water is introduced to form a solution of the resultant reaction products. Twenty grams of ethyl alcohol is then added to replace that lost by evaporation during neutralization. Upon addition of this water and alcohol two liquid phases form. The lower layer is then drawn off and 6 grams of ethyl alcohol added to the upper phase producing a second like phase separation. The combined upper layers, constituting approximately 45% by volume of the total volume of the upper and lower layers are thereafter cooled to 25 C. and filtered to free it from crystallized sodium sulfate. The sodium salt of the sulfate of the monoglyceride is thus recovered in a relatively pure state.

EXAMPLE III In this instance 10% grams of mix, as described Example I, is neutralized using ammonium carbonate. Employing similar mol ratios as in Example I, a neutralizing slurry comprising 70 grams of ammonium carbonate, 64 grams of ethyl alcohol (95%) and 60 grams of water is taken to neutralize 10! grams of the acid mix. The rate of introduction of the acid mix is such that the temperature during the neutralization maintained below 40 C. Upon the addition of suiiicient water to dissolve the 7. ammoniumsulfate formed during. neutralization the mixture readily separates into two. liquid phases. The upper layer containing the ammonium salt of the sulphonated material is drawn off and the alcohol driven off to recover the ammonium salt of the organic sulphonate.

EXAMPLE IV In this instance the procedure described in Example III is followed using ammonium bicarbonate instead of ammonium carbonate. To neutralize 100 grams of the acid mix a neutralizing slurry is used comprising 102 grams of ammonium bicarbonate in 60 grams of ethyl alcohol (95%) and 60 grams of water.

EXAMPLE V In this example 100 grams of acid mix, as described in Example I is stirred into an aqueousorganic solvent mixture comprising 66 grams of anhydrous sodium carbonate in 150 grams of a liquid vehicle comprising water and isopropyl alcohol (1:1 by volume). The temperature during the neutralization was maintained at about 35-40 C. by controlling the rate of addition of the acid mix into the alkaline slurry.

EXAlVIPLE VI Example V is repeated and the sodium salt of the organic sulphonate material separated from the sodium sulfate by adding 60 grams of Water and 36 grams of isopropyl alcohol to obtain a liquid phase separation. The upper liquid layer containing most of the neutralized organic sulphonate material is separated from the lower aqueous sodium sulfate layer by drawing oil the lower layer and evaporating the solvent from the upper layer.

EXAMPLE VII A quantity of sulphonated dodecyl alcohol containing free sulfuric acid is neutralized with the requisite amount of soda ash as described in Example I, the liquid vehicle of the alkaline slurry in this instance comprising 70% by volume ethyl alcohol and 30% by volume water. After mixing the sulphonated material and alkaline slurry together, the resultant neutralized re action mass is then adjusted to a pH of about 6.0 to 6.2, and the solvent evaporated to recover the product as a mixture of organic and inorganic sulfates.

In other runs which were made using sodium carbonate slurry to neutralize the acid mix described, wherein the aqueous-organic vehicle comprised 35% by volume of ethyl alcohol, considerable foaming was encountered and the final neutralized organic sulphonate product recovered was found to contain a lower percentage of the sodium salt of the organic sulphonate than when a larger proportion of alcohol was used. In a particular run the ether soluble fraction in the final product amounted to 6.85% by weight. In additional runs wherein the ethyl alcohol content of the alkaline slurry was reduced still further for example in one case the alcohol content being 25% by volume and another 15% by volume of the slurry, the ether soluble matter in the final product were 6.74% and 7.45%, respectively. When the alcohol content of the alkaline slurry was increased to 50% by volume, however, the ether-soluble matter was found in a typical run to be 4.44%.

When sodium bicarbonate is substituted for soda ash in the alkaline slurry the ether-soluble matter similarly increases as the proportion of ethyl alcohol in the neutralizing slurry is de creased below 50% by volume. For example, in a test run made using sodium bicarbonate in a mixture of water and ethyl alcohol to neutralize a quantity of acid mix as described in- Example I, and wherein the alcohol content was only 25% by volume, the reaction foamed considerably and although the temperature during neutralization remained below 35 C., the final product analyzed 7.26% ether-solubles. A similar run made wherein the alcohol content of the slurry was increased to 50% by volume resulted in lowering the content of ether-soluble matter in the finished prodnot to 2.93% by weight. Accordingly, where it is desired to produce a finished product having a high percent of active ingredient the proportion of organic solvent will be relatively high with respect to the water content of the alkaline mixture used to neutralize the acid sulphonate material.

Although the invention has been described and specific examples given showing how the invention may be utilized in the preparation of certain water-soluble organic sulphonated materials it is to be understood that the process may also be used advantageously in the neutralization of other acidic substances wherein similar difficulties as regards hydrolysis, decomposition reactions, and the problem of separating surfaceactive materials from inorganic salts are present.

What is claimed is:

l. The process of neutralizing acidic organic sulphonate material containing a compound having an ester linkage in the molecular structure which is hydrolyzable comprising carrying out the neutralization at a temperature above 20 C. by bringing said organic sulphonate material into contact with a neutralizing basic material which reacts therewith generating a gas producing a foamy mass containing organic and inorganic salts, said basic material comprising finely divided particles of an alkali carbonate suspended in a vehicle comprising water and organic solvent, said water being present in said vehicle in an amount within the range of about 15% to about 50% by volume.

2. The process which comprises neutralizing an acid sulfonation reaction mixture containing an organic sulfonic acid and unreacted sulfonating agent by bringing said mixture into contact with a suspension of alkaline particles in a liquid vehicle comprising water and an allphatic short chain alcohol, said water being present in said vehicle in an amount within the range of above 15% to about 50% by volume and said alkaline material comprising a salt of a strong base and a weak volatile acid which reacts with said acid sulfonation reaction mixture to produce a foamy mass containing neutralized organic sulphonate, inorganic salt and a generated gas, and adding additional water and alcohol to the re sultant neutralized mass in amounts sufiicient to form two liquid layers one of which is an aqueousalcoholic layer containing the neutralized organic sulphonate material and the other an aqueous layer containing said inorganic salt together with only a minor proportion of said alcohol and neutralized sulphonate.

3. In the preparation of the sodium salt of sulfated coconut oil fatty acid monoglycerides by the neutralization of an acidic mixture comprising sulfuric acid esters of monoglycerides of coconut oil fatty acids and free sulfuric acid, the steps comprising bringing said acidic mixture into contact with a base consisting of a slurry comprising finely divided sodium carbonate suspended in a vehicle comprising ethyl alcohol and water to form a foamy mass containing the sodium salt of sulfated coconut oil fatty acid monoglycerides, sodium sulfate and carbon dioxide gas, said water being present in said vehicle in an amount within the range of above 15% to about 50% by volume, adjusting the temperature of the resultant reaction mass to between about 30 and 40 C. and the pH to between about 10 reaction mass to cause two liquid layers to form, 15

10 one of which is an aqueous-ethyl alcohol layer containing the neutralized organic sulfate material and the other an aqueous layer containing principally sodium sulfate with minor amounts of alcohol and neutralized organic sulphonate.

ARTHUR IRA GEBHART. JOSEPH EDWARD MITCHELL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,192,721 Toone Mar. 5, 1940 2,325,320 Holuba July 27, 1943 2,511,043 Busch June 13, 1950 

1. THE PROCESS OF NEUTRALIZING ACIDIC ORGANIC SULPHONATE MATERIAL CONTAINING A COMPOUND HAVING AN ESTER LINKAGE IN THE MOLECULAR STRUCTURE WHICH IS HYDROLYZABLE COMPRISING CARRYING OUT THE NEUTRALIZATION AT A TEMPERATURE ABOVE 20* C. BY BRINGING SAID ORGANIC SULPHONATE MATERIAL INTO CONTACT WITH A NEUTRALIZING BASIC MATERIAL INTO REACTS THEREWITH GENERATING A GAS PRODUCING A FOAMY MASS CONTAINING ORGANIC AND INORGANIC SALTS, SAID BASIC MATERIAL COMPRISING FINELY DIVIDED PARTICLES OF AN ALKALI CARBONATE SUSPENDED IN A VEHICLE COMPRISING WATER AND ORGANIC SOLVENT, SAID WATER BEING PRESENT IN SAID VEHICLE IN AN AMOUNT WITHIN THE RANGE OF ABOUT 15% TO ABOUT 50% BY VOLUME. 